'Sugar' Shane hangs up his gloves aged 40

Five-time world champion Shane Mosley is retiring from boxing, with the veteran fighter admitting he "just can't do it anymore".

Mosley, who won titles across three different weights, is leaving a 19-year career behind him to train his 21-year-old amateur son, Shane Mosley Jr, and join the promotional world.

"Good morning everybody. Just want to thank you for showing me so much love," Mosley tweeted. "Had a great career and loved every moment of it, win, lose or draw."

Mosley, who turns 41 in September, later told ESPN.com: "I'm going to leave it alone. I'm good. I'm going into the promotional world; I'm training my son. It was a helluva career. I'm happy for all the great memories and all the great fighters that I fought. Now it's time to give back. I'm ready to train my son full-time now."

The American, who was never knocked out, was widely considered the No. 1 fighter in the world in the early 2000s. His career-defining moment was arguably when he beat Oscar de la Hoya for the WBC welterweight title in 2000, before he again triumphed over the 'Golden Boy' in 2003 to claim the light-middleweight belt.

"I have to credit a lot of those wins to [the late] Genaro Hernandez and Zack Padilla," Mosley added. "They were both world champions fighters and they sparred with me every day and molded me into the fighter I was. So did my father [Jack, who also trained him]. I owe a lot to him.

"Being recognised as pound-for-pound, especially when Roy Jones was there at that time, was an honour. To be considered in the same breath as Roy was great for me. Not many people can say they were the pound-for-pound best, but I'm one of those people."

As his infamous speed and power deteriorated over time, Mosley suffered tough defeats and bows out having lost three of his last four fights, including a reverse against Manny Pacquiao in 2011.

After losing to rising Mexican star Canelo Alvarez in May, Mosley said he realised it was time to call it a day. "That's life, that's getting older. When you get older, you see what happens. You think you can do things. You see stuff that you think you can do, that you want to do, but you just can't do it anymore."

He retires with a record of 46 victories, eight defeats and one loss, with 39 of his wins coming by way of knockout.